Disconnect switch

ABSTRACT

A load-disconnect switch comprises an elongated switch-pin structure which is linearly movable longitudinally between closing and opening positions. In the closing position the switch-pin structure forms an electrical connection between a stationary contact member and a stationary slide contact. For interrupting the current the switch has a load switching assembly which comprises the stationary slide contact and the correlated end of the switch-pin structure, as well as two insulating tubes of which one is movable and surrounds the switch-pin structure, whereas the other tube is stationarily connected with the slide contact and surrounds the movable tube. The movable tube is coaxially and fixedly joined with the movable switch-pin structure. Auxiliary contact means temporarily connect the switch-pin structure with the stationary contact member during the initial part of the switch-pin travel toward the open position.

United States Patent [72] Inventors llelnz-llelmut Schramm;

Claus Kessler; Paul Kuenzle; llans-Karl Renter, all of Berlin, Germany [2| Appl. No. 780,731 [22] Filed Dec. 3, 1968 [45] Patented June 22, 1971 [73] Assignee Siemens Aktiengesellschalt Berlin, Germany [32] Priority Dec. 12, 1967, Feb. 16, 1968 [33] Germany [31 Pl690ll3.6 andP 1690-1431 [54] DISCONNECT SWITCH 36 Claims, 5 Drawing Figs.

[52} US. Cl. 200/146, 200/148 [51] Int. Cl Hlh 33/82 [50] FieldolSearch 200/146, 148, 148.1, 166 B, 48,149.1

[56] References Cited UNITED STATES PATENTS 2,367,934 1/1945 Flurscheim... 200/ 148 2,679,567 /1954 Kradel 200/ 146 5e 28 g as as 50 a7 a 39 5147Ka\52 22 20 FOREIGN PATENTS 400,716 11/1933 Great Britain 200/146 1,131,567 2/1957 France 200/148 Primary Exam inerRobert K. Schaefer Assistant Examinerl-l. J. l-lohauser AttorneysCurt M. Avery, Arthur E. Wilfond, Herbert L.

Lerner and Daniel .1. Tick ABSTRACT: A load-disconnect switch comprises an elon gated switch-pin structure which is linearly movable longitudinally between closing and opening positions. in the closing position the switch-pin structure forms an electrical connection between a stationary contact member and a stationary slide contact. For interrupting the current the switch has a load switching assembly which comprises the stationary slide contact and the correlated end of the switch-pin structure, as well as two insulating tubes of which one is movable and surrounds the switch-pin structure, whereas the other tube is stationarily connected with the slide contact and surrounds the movable tube. The movable tube is coaxially and fixedly joined with the movable switch-pin structure. Auxiliary contact means temporarily connect the switch-pin structure with the stationary contact member during the initial part of the switch-pin travel toward the open position.

PATENTEUJUNZZISH 35 5,1304

SHEET 2 OF 2 Fig.3

W ,.,.,r 122 2 v I 121 I 113 l q 120 DISCONNEC'I SWITCH Our invention relates to disconnect switches, in particular to those of the type known from the German Pat. No. 877,469.

The known disconnect switch has a contact pin moved along a straight line and providing in its switch-closing position an electrical interconnection between a stationary contact member and a stationary slide contact which slidably guides the contact pin. This disconnect switch has, at the region of the slide contact at the end of the contact pin coacting therewith, a movable insulating tube surrounding the contact pin and a stationary insulating tube connected with the slide contact and surrounding the movable insulating tube. When this disconnect switch is closed; the movable insulating tube rests against the contact .pin. The flow of current between the stationary contact member and the end of the contact pin coacting therewith takes place in a normal manner by way of a springy'contacting leaf. At the other end of the contact pin swingable'contact levers coact with the latter, and the swingable'contact levers are carried by the slide contact and engage the contact pin when the switch is in its closed position. In

order to open the switch, the movable insulating tube is advanced to a location between the swingable contact levers and the contact pin, while the contact pin itself remains in the switch-closing position thereof. The end of the movable insulating tube distant from the stationary contact then operates as a control which displaces the swingable contact levers away from the contact pin so that arcing is created therebetween. This arcing between the contact pin and the slide contact is directed to an extent of approximately one-half into the narrow annular space between the movable insulating tube and the stationary insulating tube which surrounds the movable tube, so that the gases liberated out of the insulating tubes exert a strong arc-extinguishing action. Thus, the gases which develop during the switching operations escape from the annular gap between the pair of insulating tubes, inasmuch as the tubes are open at their ends which are directed toward the stationary contact. After a predetermined extent of movement, during which the arc is normally extinguished, the movable contact pin follows the movable insulating tube. In this way the required visible air gap between the stationary contact and the end of the movable contact pin adjacent thereto is provided.

It is a primary object of our invention to provide an improvement in a disconnect switch of the above general type.

Thus, it is an object of our invention to provide a disconnect switch capable of having its dimensions reduced as compared to conventional disconnect switches.

Also, it is an object of our invention to increase the circuitbreaking capacity of the switch not only with respect to the capability of extinguishing arcs of high current intensity but also with respect to operations with relatively small currents without encountering excessive potentials.

In accordance with the invention the disconnect switch includes an elongated axially movable primary contact means which is shiftable between switch-closing and switch-opening positions. A pair of opposed stationary contact means coaxially arranged with respect to each other are also situated coaxially with respect to primary contact means. One of these stationary contact means slidably supports and guides the primary contact means for movement between its positions while the other of the stationary contact means is engaged by primary contact means in the switch-closing position of the latter. The primary contact means is displaced beyond and is out of contact with this other stationary contact means when the primary contact means is in its switch-opening position. The primary contact means includes inner elongated electrically conductive components directly engaging the pair of stationary contact means when the primary contact means is in its switch-closing position. The primary contact means further includes an outer tube of insulating material surrounding the inner components and fixed to them for axial movement with the inner components. Thus, the outer tube of insulating material also moves axially, and there is no relative axial movement between the innercomponents and outer insulating tube of the primary contact means. A secondary contact means coacts with the primary contact means and with the other of the stationary contact means for temporarily maintaining an electrical connection therebetween bridging a gap which initially forms .between this other stationary contact means and the primary contact means during the initial part of the movement of the latter from its switch-closing position toward its switch-opening position.

I The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. I is a partly sectional longitudinal elevation of a disconnect switch of our invention, the section of FIG. 1 being taken in a vertical plane which contains the axis of the primary contact means;

FIG. 2 is a transverse sectional elevation of the disconnect switch of FIG. I as seen when looking from the left toward the right with the transverse'section taken transversely through the primary contact means and with the base structure being fragmentarily illustrated;

FIG. 3 is a longitudinal sectional elevation similar to FIG. 1 of another embodiment of a disconnect switch according to our invention;

FIG. 4 schematically illustrates in a longitudinally sectional elevation the disconnect switch of FIG. 3 in the switch-open position; and

FIG. 5 is a fragmentary transverse sectional elevation taken on an enlarged scale as compared to FIGS. 3 and 4 and showing details of the manner in which insulating components are connected to each other and surround and coact with the electrically conductive components.

Referring to FIGS. I and 2, an insulating covering which covers the stationary contact means 7, leaving certain portions thereof uncovered, as pointed out below, is not illustrated in FIGS. 1 and 2 for the sakeof clarity.

In FIGS. 1 and 2, only one pole of the disconnect switch is illustrated. As is conventional, the device has, however, three poles, so that it can be used in a three-phase line, particularly with medium voltages of l030 kv.

The disconnect switch has a supporting structure in the form of a sheet metal frame 1 having a pair of opposed parallel sidewalls 2, the frame having its sidewalls connected by atransverse central frame member 3 having the profile which is clearly visible at the lower portion of FIG. 1. A pair of identical support means 4 made of an electrically non conductive insulating material are respectively fixed symmetrically with respect to each other to the middle frame part 3 and extend upwardly therefrom in the manner indicated most clearly in FIG. 1. From their bottom ends which are directly fixed to the frame 3, the insulating supports 4 extend upwardly while being inclined away from each other so that the upper ends of the symmetrically arranged pair of insulating means 4 are situated at a greater distance from each other than their lower ends which are at the grounded side of the assembly. The upper ends of the pair of support means 4 provide for all of the contact means described below a unipolar current path which is insulated with respect to ground potential. The pair of insulating support means 4 are each of rectangular cross section in a horizontal plane. The distance of the pair of supports 4 from each other at their ground-side ends is approximately only half as great as the distance between the upper ends of the pair of support means 4 in the region of the current path.

The right insulating support 4 of FIG. 1 fixedly carries a stationary contact means 6 while the lefi support means 4 of FIG. 1 fixedly carries a second stationary contact means 7. The pair of contact means 6 and 7 are coaxial with respect to each other and have inner exposed cylindrical surfaces to be engaged by the primary contact means referred to below. Thus, the pair of stationary contact means 6 and 7 are both in the form of electrically conductive metallic rings fixedly carried about by the pair of support means 4. The left stationary contact means 7 of FIG. 1 forms a contact means which slidably supports and guides the primary contact means 8 for axial movement, this primary contact means 8 having its axis coinciding with the common axis of the pair of stationary contact means 6 and 7, and in the illustrated position of the parts, shown in FIG. 1, the pair of stationary contact means 6 and 7 are electrically interconnected by the primary contact means 8 so that the parts are shown in the switch-closing position in FIG. I. The primary contact means 8 is shifted by a swinglever means 10 made up of an insulating material. This lever means 10 itself is clamped onto a metal guide shaft 11 which extends transversely through and is supported for rotary movement by the pair of sidewalls 2 of the sheet metal frame 1.

The stationary contact means 6 consists of a ring 13 having a mounting flange by which it is fixed to the upper end of the right insulating support means 4 of the FIG. 1, by way of unillustrated bolts, for example. The inner cylindrical contact surface of the rigid ring 13 of the stationary contact means 6 defines the cylindrical bore 14. At its side which is directed away from the primary contact means 8 the ring 13 of the stationary contact means 6 is provided with a pair of projections 15 and 16 which are fixedly connected and support a sheet metal strip 20 which in turn carries the stationary component 21 of a secondary contact means. The upper surface 22 of the ring 13 is a connecting surface to which conductors are connected by way of unillustrated bolts or the like, so that in this way the ring 13 of the stationary contact means 6 is connected into the electrical circuit.

The opposed stationary contact means 7 which slidably supports and guides the primary contact means for movement toward and away from the stationary contact means 6 is composed of a rigid metallic electrically conductive ring 24 the inner cylindrical surface of which is exposed to make contact with the primary contact means, and this inner cylindrical surface defines the cylindrical bore 25. The bores 14 and 25 are not only coaxial, but in addition they have the same diameter.

The ring 24 of the stationary contact means 7 is provided at its bottom end with a mounting flange 26 (FIG. 2), and by way of bolts 27 this mounting flange is fixed to the top surface of the left insulated support means 4 of FIG. 1, so that in this way the stationary contact means 7 is fixedly supported. The top surface of ring 24 is flattened so that it forms a connecting surface for electrical conductors which can be pressed against this flattened upper surface of the ring 24 by way of a bolt, for example, which can be threaded into the internally threaded bore 28 which is formed in the ring 24 andextends into the latter from its upper flat surface.

The axially movable primary contact means 8 includes an outer tube 30 of electrical insulating material shown in longitudinal and transverse sections in FIGS. 1 and 2 respectively. This primary contact means 8 further includes inner elongated electrically conductive components 31 in a form of elongated bars of rectangular cross section (FIG. 2). The outer insulating tube 30 of the primary contact means 8 is formed at its inner surface with a plurality of axially extending grooves which respectively receive the metal bars 31 of the primary contact means, so that in this way the positions of the metal bars 31 are determined by the outer insulating tube 30. In the illustrated example there are 12 metal bars 31 uniformly distributed about and extending parallel to the central axis of the tube 30 which coincide with the axes of the rings 13 and 24. These metal bars 31 may be considered as forming axial sections of a tube 32 which is axially slotted to define the separate bars 31. The outer ends of each bar 31 are curved outwardly away from the axis of the tube 30, so that each bar 31 may be considered as having a U-shaped configuration, and these outwardly c'urved ends 34 and 35 of each bar 31 are symmetrically arranged with respect to each other. It is these ends 34 and 35 which directly engage the inner cylindrical surfaces of the rings 24 and-13. The several bars 31 are preferably made of a springy material of good electrical conductivity such as, for example, a suitable copper-chrome alloy.

A pressing means is provided for pressing several bars 31 outwardly away from the axis of the tube 30 into the grooves of the latter. This pressing means includes the interior metal tube 37 situated within the tube 30 and surrounded by the tube 32 composed of the bars 31. This interior metal tube 37, which is made of a springy metal, is provided with a pair of circumferentially extending outwardly bulging beads 38 and 39 which press in an outward direction against the inner surfaces of the several bars 31, so as to resiliently hold the latter within the grooves of the tube 30. Because of this manner of pressing the bars 31 into the grooves of the tube 30, the free ends 34 and 35 of the several bars 31 will have an increased contact pressure with the pair of stationary contact means 7 and 6, respectively. The positions of the beads 38 and 39 is calculated in such a way that the forces tending to pull on the bars 31 at their regions between the-beads 38 and 39 are at least substantially compensated by forces which tend to pull on the bars 31 at the regions thereof which extend outwardly beyond the beads 38 and 39. Thus, with uniform current distribution the pressure of the bars 31 at the surfaces which define the bores 14 and 25 will become greater and not smaller with an increasing current intensity.

In addition, the outer insulating tube 30 has inserted into its left end region, as viewed in FIG. 1, an arc-contact ring 40. This arc-contact ring 40 extends from its flange 41 situated at the left end of the tube 30 as viewed in FIG. 1, and having an exterior diameter which is equal to the exterior diameter of the tube 30, up to the region of the bead 38 along the interior of the tube 30 where the arc-contact ring 40 has a smaller diameter.

The secondary contact means includes in addition to the stationary component 21 referred to above a movable component 42 in the form of an elongated pin assembly situated within the metal tube 37 and extending coaxially along the interior thereof.

At its right end, as viewed in FIG. 1, the movable component 42 of the secondary contact means has a tip 43 which coacts with the stationary component 21 of the secondary contact means. This component 21 may be in the form of a hollow truncated cone which tapers toward the left, as viewed in FIG. I, and which is longitudinally slit so that it has a plurality of springy tongues terminating at their left ends, as viewed in FIG. 1, in inwardly directed projections, respectively. The right end of the stationary component 21 of the secondary contact means is fixed with a threaded stud 45 which extends through a suitable opening of the strip 20 and which carries a nut 46 so that in this way the stationary component 21 of the secondary contact means is fixed in its proper position. The inner projections 47 at the smaller end of the component 21, at the several tongues thereof, respectively, engage behind the thickened conical tip portion 48 at the right extremity of the movable component 42 of the secondary means, the part 43 having directly behind the conical tip, 48 a shank of a smaller diameter than the left end of the conical tip 48, so that the latter can insert itself into the space surrounded by the springy tongues of component 21, displacing these tongues apart from each other until their projections 47 snap behind the tip 48 to locate this secondary contact means 42, 21 in the position illustrated in FIG. 1. The coaction of the springy tongues with the tip 48 of the tip assembly 43 of the secondary contact means provides a well-defined holding force for the secondary contact means. The thickened tip 48 has just at the left of its pointed right end its largest diameter and then tapers slightly toward the left as viewed in FIG. 1, so that when a given force urges the pin 42 to the left, as viewed in FIG. 1, the tip 48 will also displace the springy tongues of stationary component 21 apart from each other and the component 42 will be released from the component 21 to move to the left and thus open the contact made by the secondary contact means 42, 21.

The end region component 42 which is opposed to the tip assembly 43 thereof is provided at its left extremity, as viewed in FIG. 1, with an outwardly directed flange 49 having a right surface, as viewed in FIG. 1, against which a coil spring 50 is seated. Thus, the left end of the coil spring 50 engages the right surface of the flange 49 fixed to the left end of the pin 42, as viewed in FIG. 1. This spring 50 is coiled about pin 42 and extends axially along the exterior thereof all the way from the flange 49 to the region of the tip assembly 43 where the right end of the coil spring 50 engages the left end 51 of a sleeve 52 which flares outwardly at its right end, as viewed in FIG. 1, which is made of an electrically conductive metal, and which is threaded directly into the interior of the metal tube 37 in the manner indicated in FIG. 1. The opposed end of the metal tube 37 is closed by a plug 54 made of an insulating material and also threaded directly into the interior of the tube 37.

The-left end flange 51 of the sleeve 52 surrounds the shank of the pin 42 so that the sleeve 52 acts as a guide for the movable component 42 of the secondary contact means. Of primary importance, however, is the fact that because of its rounded exterior surface this sleeve 52 coacts with the stationary contact means 6 in order to provide an electrical field that for the most-part is homogeneous. This gives to the structure of our invention a high dielectric strength in the switch-open position and short arc-over length during displacement of the disconnect switch to'its closed position. Moreover, the sleeve 52 absorbs the pulse of current which occurs when closing the switch on a short circuit, so that the sleeve 52 in this way protects the bars 41 of the primary contact means 8.

At the opposed stationary contact means 7, the structure of our invention includes a stationary tubular member 55 made of an insulating material which is preferably polyoxymethylene, and this tubular member 55 is screwed or otherwise fixed to the stationary contact means 7 at the end of the latter which is directed away from the stationary contact means 6. The tube 55 is closed at its left end, so that it forms at contact means 7 an enclosure which is completely cut off from the outer atmosphere except for gas-discharge openings referred to below. At the interface 56 between the tube 55 and the metal ring 24, where these components butt against each other, the interior of the tube 55 is formed with an annular recess 58. From this recess 58 extend passages 59 which communicate on the one hand with the interior of the recess 58 and on the other hand with the gas-discharge openings 60 formed in an outer flange of the component 52 and extending axially to communicate with the outer atmosphere. Thus, gas which develops in the interior of the disconnect switch of our invention can escape to the outer atmosphere by blowing out through the discharge passages 60 which communicates with the recess 58 at the interior of the enclosure 55 through the openings 59, respectively. These passages or openings 60 direct the gases away from the stationary contact means 7.

The axial length of the annular recess 58, in the illustrated embodiment of our invention, is on the order of one-sixth the diameter of the tubular enclosure 55, this tubular closure having at its interior the diameter which is equal to the diameter of the bore 25. In order to provide a precise coincidence between the axis of the bore 25 and the axis of the hollow interior 63 of the component 55, the latter has its recess 58 interrupted by a plurality of axially extending projections 64 which extend slightly beyond the interface 56 into engagement with a step or shoulder formed at the left end of the bore 25 in the ring 24,'as viewed in FIG. 1. In this way a precise centering of the tubular component 55 is achieved.

At the side of the stationary contact means 7 which is opposed to the side carrying the component 55 a covering 65 of an insulating material is fixed as by being bolted to the stationary contact means 7, and this insulating covering 65 also is made of polyoxymethlene. As may be seen from FIG. 2 in particular, the insulating covering 65 is provided with axially extending openings 66 to receive four bolts by means of which the insulating covering 65 is fixed to the stationary contact means 7, and these four openings 66 are all visible in FIG. 2. The insulating covering 65 is provided at its interior with a diameter which is slightly greater than the outer diameter of the outer sleeve 30 of the primary contact means 8. The covering 65 extends, as indicated in FIG. I, over approximately one-third of the distance between the stationary contact means 7 and the stationary contact means 6. In this way there is defined between the tube 30 and the tubular covering 65 which surrounds the tube 30 an elongated cylindrical narrow gap 67 which acts in a manner of a labyrinth seal. In order to center the tubular coverings'65 with respect to the ring 24, this ring has at its right face, as viewed in FIG. 1, an inner annular projection 68 received in a mating annular recess formed at the leftend of the tubular. covering member 65.

The swing-lever means 10 is also made of polyoxymethylene. This lever means has a pair of parallel arms defining between themselves a space which receives the primary contact means 8, and these arms are respectively formed with the elongated slots 70 which arerespectively surrounded by the strengthening ribs 71. The lower, end of the swing lever 10 where the arms thereof are interconnected by a transversely extending bored portion of thelever means 10 is also slotted to form a pair of projections 72 which extend around and axially along the drive shaft 11'. These projections 72 have a configuration matching that of the drive shaft 11 so that at the flattened surface 74 of the latter, the right portion 72 of the lever means 10 will have a good contact.

This driving engagement between ,the drive shaft 11 and the lever means 10 is particularly enhanced by a clamping plate 75 engaging exterior surfaces of projections 72 and drawn toward each other by the bolts 76, so that in this way the portions 72 clamp the lever means 10 onto the drive shaft 11 for rotary movement therewith.

The disconnect switch of our invention is shown in FIG. 1 in the position where the switch is closed. The current flows from the stationary contact means 6 through the ends 35 of the bars 31 to the opposite ends 34 of the latter. From these ends 34 the current can be taken off by the stationary contact means 7.

In order to displace the disconnect switch of our invention to its open position, the swing-lever means 10 is turned by way of the shaft 11 in a counterclockwise direction, as viewed in FIG. 1. The outer tube 30 carries coaxial metallic slide pins coaxially fixed to the exterior surface of the tube 30 along an axis normal to axis of the tube 30, and these slide pins are respectively received in the slots 70 of the arms of the lever means 10. Therefore, as the latter swings the slots 70 toward the left, as viewed in FIG. 1, the movement is transmitted through these pins to the tube 30 which thus causes the entire primary contact means 8 to be displaced toward the left, as viewed in FIG. 1. As a result arcing will occur when the ends 34 of the bars 31 move'beyond the left end of the stationary contact means 7 which slidably supports and guides the primary contact means 8. However, at the opposed end of the disconnect switch where the right end of the primary contact means 8 moves beyond the stationary contact means 6, as viewed in FIG. 1, there will be a gap between the primary contact means 8 and stationary contact means 6, but initially the secondary contact means 42, 21 acts to bridge this gap maintaining the primary contact means 8 still electrically connected with the stationary contact means 6 through the secondary contact means 42, 21.

The arcing commutates during the further movement of the switch toward its open position onto the arc-contact ring 40 which is mounted on the tube 30 of insulating material. The are is extinguished after a relatively short extent of movement of the primary contact means 8. This extinguishing the arcing takes place with relatively small currents for the most part as a result of the fact that the plug 54 functions as a piston and compresses air within the tubular enclosure 55 so that this compressed air blows onto and extinguishes the arcing. With larger currents, the tubes 30 and 55 split off the gas as a result of the heat generated by the arcing. This gas blows over the are which burns in the narrow annular gap between the tube 30 and the tube. 55, before the gas flows through the annular recess 58 and the openings 59 to the gas-discharge passages After the arcing is extinguished, the continued movement of the primary contact means 8 to the left toward its switch-,open

position results in continued compression of the spring 50 since the left end 51 of the sleeve 52 continuously advances the right end of the spring 50 toward the flange 49 against which the left end of the spring 50 presses, as viewed in FIG. 1, the right end of the component 42 of the secondary contact means being retained by the coaction between the springy tongues of the stationary component 21 and the pointed tip 48, as pointed out above. However, during the movement of the primary contact means 8 toward its switch-open position, the spring 50 becomes compressed to an extent sufficiently great to overcome the force with which the springy tongues of component 21 retain the tip 48, so that the spring 50 will suddenly expand upon overcoming the force of the stationary component 21. The pin 42, which is of a relatively small mass, is thus very rapidly advanced toward the left, as viewed in FIG. 1, now following the movement of the primary contact means 8, so that the full dielectric strength of the insulating gap between the primary contact means 8 and the stationary contact means 6 becomes effective.

In order to return the disconnect switch of our invention to the opposed switch-closing position thereof, the swing-lever means 10 is turned in a clockwise direction by way of the drive shaft 11, as viewed in FIG. 1, with the result that the primary contact means 8 is displaced toward the right and when the primary contact means engages the stationary contact means 6 the movable component 42 of the secondary contact means will also simultaneously engage the stationary component 21 of the secondary contact means. A preliminary arc-over will occur only at the sleeve 52 because the ends 35 of the bars 31 and the pin 42 are dielectrically in the shadow of, or subordinate to, the sleeve 52. As a result, the disconnect switch of our invention will have an exceedingly good circuit-opening capability as well as a high circuit-closing capability.

According to the second embodiment of our invention which is illustrated in FIGS. 3-5, the disconnect switch further carries out our inventive concept by covering the pair of opposed stationary contact means 6 and 7, particularly at their sides which are directed toward each other, with components made of insulating material, leaving exposed only metal surfaces for making the electrical connections at those parts of the pair of stationary contact means which are directed away from grounded components. Thus, only those surface areas of the metallic components of the pair of stationary contact means are exposed which are required for the functioning of the disconnect switch. 'All other areas are covered with insulating material so as to be dielectrically unloaded. In this way it is possible, as tests have demonstrated, to achieve a dielectric strength which is on the order of approximately 30 percent higher than would otherwise be possible.

This embodiment of our invention which includes the contact components embedded in insulating material furthermore, achieves in a most surprising way a reduction in the cost of manufacture of the disconnect switch. Thus, it has been found that the metallic components can have a simplified construction because the parts thereof normally required for fastening and mounting the metal components can be eliminated. The fastening structure is located at the insulating components and cost much less than a structure where the fastening components form part of the metal parts. The reason for this is that the insulating components can be manufactured according to plastic casting, injection molding, or extruding methods at a cost which is far less than the corresponding cost of metallic components even if the plastic components have a relatively complex configuration. It then becomes possible to fixedly mount the metal components on the plastic components with only a few simple undercuts, providing, for example, a dovetail type of connection.

An insulated tubular covering 65 of the type shown in FIG. 1 and described above can also be included in the embodiment of FIGS. 3-5. The insulating material can additionally serve with the embodiment of FIG. 3, however, to cover the stationary contact means which slidably supports and guides the primary contactmeans in a voltage-resistant manner at all .8". areas except the surface which must be connected to electrical conductors and the inner contact surface required to be engaged by the inner bars of the primary contact means.

In order to increase the dielectric strength, metal components which extend through interfaces formed between butting surfaces of insulating components can be surrounded at the region of these interfaces with an equipotentially extending surface of insulating material. This insulating surface can itself be formed as part of a component of insulating material. It is possible, however, also to use in addition an insulating tube which surrounds the metal component. In some cases a simple insulating sleeve will suffice for this purpose.

The disconnect switch of FIG. 3 is designed for a voltage on the order of, for example, 20 kv. It is illustrated in FIG. 3 in the switch-closed position. I

FIG. 4 schematically illustrates the switch of FIG. 3 in the same plane as FIG. 3 but in the switch-open position. FIG. 5 shows in detail how the stationary contact means which supports and slidably guides the primary contact means is fixedly mounted. I

Thus, as may be seen from FIGS. 3 and 4, the disconnect switch illustrated therein includes a pair of insulating support means 102 carried by the sheet metal frame 101. The right support means 102 of FIGS. 3 and 4 carries the stationary contact means 103 made up of a ring of copper which in cross section is approximately rectangular and having a rounded edge directed toward the opposed, coaxial stationary contact means 105 which serves to support and slidably guide the primary contact means of this embodiment. This ring 103 has an upper flat exposed surface 104 to which electrical conductors can be connected, this surface 104 forming part of a projection of the stationary contact means 103 which is directed away from the frame 101. The stationary contact means 103 is fixed to a component 120 of insulating material. This insulating component 120 fixedly carries a mounting member 121 for the slotted stationary component 113 of the secondary contact means, this stationary component 113 having springy tongues as described above for the component 21. The component 121 is received in a suitable recess fonned in the insulating component 120, as is indicated in the sectional illustration of FIG. 3. The hollow space resulting from the recess which receives the mounting component 121 is covered by an insulating plate 122.

The left stationary contact means of FIGS. 3 and 4 is carried by the left insulating support means 102 of FIGS. 3 and 4 and is provided at its side which is directed away from the frame 101 with an exposed surface 106 to which electrical conductors can be connected. All other surfaces of the stationary contact means 105, except its inner cylindrical surface, are covered with components of insulating material. These components include the insulating covering 125 having the tubular projection 126 extending from the stationary contact means 105 toward the stationary contact means 103. This insulating covering 125 is fixed on the left support means 102 of FIGS. 3 and 4. By way of suitable through-bolts, the covering 125 of insulating material is fixed with the tubular enclosure 116 which corresponds to the tube 55 of FIG. 1. As is apparent from the above description in connection with component 55, the component 116 forms part of the device for extinguishing the arcing.

The primary contact means 107 also includes a plurality of axially extending inner bars received in inner axial grooves of the outer insulating tube 109 of the primary contact means 107. The inner metal tube 111 acts as a pressing means for pressing the bars 110 outwardly from the axis of the tube 109 into the inner axial grooves thereof, and in this embodiment the outer tube 109 and components 110 are fixed to each other for axial movement as a unit. The interior of the metal tube 111 which has outwardly bulging circumferential beads pressing against the bar 110, accommodates the movable component 112 of the secondary contact means. Thus, this movable component 112 coacts with the stationary component 113 of the secondary contact means precisely in the same way that the components 42 and 21 coact with each other. At its left inner periphery the stationary contact means 105 is formed with a bevelled surface 114 which facilitates the movement of the primary contact means 107 into and along the interior of the stationary contact means 105.

The swing-lever means 108 which is made of insulating material coacts with the primary contact means 107, in precisely the same way that the swing-lever means of FIG. 1 coacts with the primary contact means 8, so that when the drive shaft of FIG. 3 turns with respect to the frame 1 in a counterclockwise direction, as viewed in FIG. 3, the arms of the lever means 108 107 will swing toward the left to displace the primary contact means 107 from its illustrated switch-closing position to the switch-opening position thereof shown in FIG. 4. The arc which is created at this time between primary contact means 107 and the stationary contact means 105 is quickly commutated from the bars 110 onto the arc-contact ring 115 which corresponds to the arc-contact ring 40 and acts in the same way.- During the initial part of the movement of the primary contact means 107 to its switch-open position, the

secondary contact means remains closed to bridge the gap between the primary contact means and the stationary contact means 103, as indicated in dot-dash lines in FIG. 4.

The arcing is extinguished by the flow of gases, these gases discharging out of the tubular enclosure 116 through the gasdischarging openings 117 through the passages formed between the openings 117 and the interior of the enclosure 116 as described above in connection with FIG. 1. Moreover, the plug 118 which corresponds with the plug 54 and is located at the left end of the outer tube 109 of FIG. 3 acts as a piston to compress air in the enclosure 116, this compressed air also blowing over the arcing to contribute to the extinguishing thereof.

The metal sleeve 119 at the other end of the primary contact, means 107, corresponding to the metal sleeve 52 described above, acts in the same way to assure a uniform distribution of the electrical field. As a result, upon closing of the switch only relatively short arc-over lengths will occur.

As may be seen from FIG. 5, the stationary contact means 105 is in the form of a simple metal component. It consists only of the illustrated ring having the projection 128 forming the top connecting surface 106 for electrical conductors. For this purpose the stationary contact means 105 is formed with the downwardly directed threaded bore 130 to receive a connecting screw. The projection 128 is of a symmetrical configuration provided on both sides with undercuts 132 and 133. By way of these undercuts, it is possible for the contact means 105 to be fixedly held in the insulating body 125 which ini tially is bolted to the left insulating support means 102 of FIG. 3 by way of the bolts 135 shown in FIG. 5. After the metallic ring which forms the stationary contact means 105 has been snapped into the insulating body 125, suitable through-bolts extend through the openings 136, 137 and 138, visible in FIG. 5, as as to provide the interconnection between the insulating covering 125 and the tubular enclosure 116. In this way the stationary contact means 105 is covered on all sides by insulating material, only the contact surface 106 and the inner cylindrical surface of the contact means 105 being exposed.

The stationary contact means 103 is insulated in a corresponding manner, so that only the side of the contact means 103 directed toward the contact means 105 and the connecting surface 104 remain uncovered, this connecting surface 104 being directed away from the grounded components.

FIG. 5 illustrates how metal components such as the screws or bolts 135 extend through the interface fonned at those surfaces of support means 102 and insulating covering 125 which butt against each other. These metallic components 135 are surrounded by insulating sleeves 140, respectively, which extend across the interface between the butting surfaces of the insulating components, as shown at the lower left portion of FIG. 5, to form in this way a tubular insulation along an equipotential surface. In this way discharging from the screws or bolts 135, which have a fleeting potential, is avoided and thus stressing of the butting surfaces of the interface between support means 102 and insulating covering is prevented.

It is to be noted that all of the insulating components, with the exception of the insulating support means 4 and 102, are made of polyoxymethylene. This latter material has proved to be outstanding in all tests and also is highly suitable with respect to the working thereof.

With the disconnect switch of our invention, the common movement of the inner bars and outer insulating tube of the primary switch means results in a shortening of the arc length. As contrasted with known disconnect switches, burning of part of the arc in the interior of the movable insulating tube is prevented, this latter type of functioning contributing nothing to extinguishing of the arc. The reduction in the arc length prevents thermal stressing of the insulating tube. Furthermore, this construction of our invention is of advantage inasmuch as the outward flow of gases is'reduced and thus thedimensions can be maintained smaller than what otherwise would be possible.

A further advantage of the disconnect switch of our invention resides in the fact that the energy required to accelerate the moving masses during operation of the switch can be smaller than withconventional, known switches. The reason for this is that the speed of movement of the primary switch means during opening of the switch need not be very great. It is of advantage to provide an arrangement where the arc has available several zero points through which it can pass to afford locations where it can be extinguished without creation of overvoltages. However, it is required that the gap between the stationary contact means and the primary contact means be created as rapidly as possible, so that the electrical stressing of the insulating components be maintained as small as possible. This latter result is achieved with our invention in a manner which is far better than with conventional switches. The primary switch means is moved during switch-loading. After the interruption in the current, in order to achieve the required dielectric strength it is only necessary to open the relatively light secondary switch means; Inasmuch as the latter is only stressed for an exceedingly short time, it can be ,made of components of relatively small mass so that even with relatively small driving forces a high degree of acceleration can be achieved.

The secondary contact means of our invention bridges the gap which initially forms between the primary contact means and the stationary contact means away from which the primary contact means moves upon opening of the switch. It is to be noted in particular that the secondary contact means is surrounded by the primary contact means and the stationary contact means engaged by the primary contact means when the switch is closed, so that a separate space to accommodate the secondary contact means is not required and in this way a considerable reduction in the space required by the switch and an increase in the compactness thereof are achieved.

With the secondary contact means of our invention it is only necessary that the springy force of the stationary component be somewhat less than the maximum spring force of the coiled spring during compression thereof when the primary contact means is displaced towards its open position, so that through this simple construction the movable component of the secondary contact means will automatically follow the primary contact means substantially at the end of the movement of the latter toward its switch-open position at the moment when the force of the compressed coil spring exceeds the force with which the slotted tapered stationary component of the secondary contact means maintains the movable component thereof in its closed position. It is, however, also possible to provide for positive displacement of the movable component of the secondary contact means away from the stationary component thereof by providing a lost-motion connection between the primary contact means and the movable component of the secondary contact means so that this latter movable component will be positively displaced with the primary contact means after the latter has moved through a predetermined distance away from its switch-closing position.

The hollow Construction of the primary contact means which enables the movable component of the secondary contact means to be accommodated in the interior of the primary contact means provides the additional advantage of making the construction more favorable from a dielectric standpoint. In addition, the tubular construction of theprimary contact means is of advantage because in this way it is possible to achieve a highly favorable current-carrying capability with a low weight.

The manner in which the bars which form the inner components of the primary contact means are mounted provides for the springy pressing of the free ends thereof against the contact surfaces of the pair of stationary contact means. Further, by pressing these bars into the grooves of the outer insulating sleeve, the circumferential distribution of the bars is determined, and the inner metal tube presses the bars outwardly into the grooves of the insulating sleeve. This assembly of the bars in the grooves of the outer insulating sleeve additionally increases the efficiency with which heat is carried away so that the current-carrying capacity is also substantially increased in this way.

The inner metaltube, of course, acts advantageously in the manner of a spring resiliently pressing the bars outwardly from the axis of the insulating tube into the grooves thereof. Thus, while such components can easily be assembled, nevertheless they are mechanically strong. By curving the outer ends of the bars outwardly so that they resiliently press against the contact surfaces of the pair of stationary contact means, they act in themselves as contact locations so that no further currenttransferring locations are required.

It is to be noted that the plug which closes the left end of the primary contact means, as viewed in the drawings, acts to protect the secondary contact means situated within the primary contact means. Not only does this plug act as a piston, in the manner described above, to achieve a'flow of compressed'air, but in addition this plug prevents the gases which develop from flowing through the primary contact means to the space where the gap is formed between the primary contact means and the stationary contact means 6 or 103 during opening of the switch.

The arc-contact ring or sleeve 40 serves to reduce the load to which the primary contact means is subjected. By extending this arc-contact ring or sleeve 40 all the way up to the bead 38,

v a good current flow between the bars 31 and the arc-contact ring 40 is achieved. Also this construction prevents sputtering from occuring in the interior of the primary contact means. The arc-contact ring 40, and the corresponding ring of the embodiment of FIG. 3, can be made of copper because as a result of its arrangement in the tube of insulating material it has a surprisingly high resistance capability with respect to thermal stressing by the arcing.

A particularly great advantage of the structure of our invention resides in the arrangement according to which the plug in the insulating tube coacts with the hollow plastic enclosure 55 or 116 to compress the air therein so as to use this latter compressed air to effect the extinguishing of the arcing. Thus, these enclosures 55 or 116 act as cylinders of air-compressing units. Because of the fact that the compressed air flows out through the discharge openings or passages which are situated in the region of the stationary contact means 7 or 105, the air flows over the are at the loaded switch location throughout the entire length thereof so that even with relatively small amounts of air a surprisingly effective extinguishing action is achieved. This latter result is achieved particularly in those cases where the switch handles relatively small currents, the arcs of which develop only small amounts of gases. in a most surprising manner it has been possible with this construction to achieve very efiective switching operations even when deal ing with intensely capacitative currents, which is to say with currents having a leading phase displacement of almost 90. in a particular construction, the axial length of the recess 58, one-sixth of the diameter of the tube 55, as pointed out above, has proved to be very effective if it is in a range from -20 mm. Testing has shown that an arrangement where the axial length of recess 58 is on the order of 10 mm. has proved to be particularly advantageous. The centering projections 64 can be spaced from each other by equal angular distances around the axis of the tube 55, and three such projections uniformly distributed about the axis of the tube are preferably provided. Such positioning projections have practically no influence on the dielectric behavior ofthe extinguishing device provided with the recess 58. In the insulating gap which forms between the primary contact means and the stationary contact means 6 or 103 there can be no arcing product with the switch of our invention because this gap between the stationary contact means and the primary contact means during opening of the switch is electrically bridged by the secondary contact means. Nevertheless, it is of advantage to provide at the stationary contact means which supports and guides the primary contact means for movement the tubular insulating covering which surrounds the outer insulating tube of the primary contact means and which defines therewith the narrow gap having a relatively great flow resistance. In this way there is an assurance that even with relatively large currents and intense development of gases no gases can reach the gap between the contact means 6 or 103 and the primary contact means. The gases which develop between the switching operations can only escape through the openings provided for this purpose. It is thus possible to direct these gases to locations which are of little dielectric criticality. This tubular covering of insulating material furthermore provides an extremely efficient guide for the primary contact means which particularly during closing of the switch acts favorably on 'a short circuit.

As was indicated above it is preferred to provide at the exterior of the outer insulating tube of the primary contact means coaxial metal projections to be received in the slots of the arms of the plastic swing-lever means. As was pointed out above, this lever means is also preferably made of polyoxymethylene. However, other insulating materials may be used in the case where such materials under the action of the arcing develop gases suitable for extinguishing the arcing without becoming dielectrically deleterious.

The flattened region of the drive shaft 11, which coacts with the swing-lever means to swing the latter, need only extend through an angular of 45-90, so that this construction is achieved at low cost.

The compact construction of the disconnect switch of our invention enables the pair'of insulating support means to be provided in such a way that they also contribute to the reduction in the dimensions of-the entire switch assembly. As was indicated above, it is possible with the structure of our invention to arrange the ground-side lower ends of the insulating support means closer to each other than their upper ends which carry the pair of opposed stationary contact means. This construction is particularly suitable for disconnect switches which require exceedingly small spaces, such as for encapsulated or fully enclosed switch assemblies. The symmetrical arrangement of the pair of insulating support means according to which they extend up angularly away from each other from their bottom ends toward their top ends is of particular advantage since this construction enables a pair of identical support means to be used, so that in this way, manufacturing costs can be maintained small.

We claim:

1. A load disconnect comprising elongated, primary contact means axially movable between switch-close and switch-open positions, a pair of opposed stationary contact means coaxially arranged with respect to said primary contact means, one of said stationary contact means slidably supporting and guiding said primary contact means for movement between said positions thereof and the other of said stationary contact means being engaged by said primary contact means in said switchclose position, said primary contact means being displaced beyond and out of contact with said other stationary contact means when said primary contact means is in said switch-open position, said primary contact means comprising an insulating tubular member, elongated electrical conductive means disposed in the hollow of said tubular member, said conductive means including tubelike holding means for fixedly holding the same with respect to said tubular member, said coning means for receiving said primary contact means, and auxiliary contact means movably mounted within said tubelike =holdi'n'g means and coacting with said conductive means and H said other stationary contact means for temporarily maintaining an electrical connection therebetween by bridging a first gap that forms between said other one of said stationary contact means and said other one of said ends of said conductive me ns during the initial part of the movement of said primary 3 [cam-set means from said switch-close position to said switchopen position, whereby said primary contact means moves with respect to said are extinguishing means for developing an air blast to extinguish the are appearing across a second gap that forms between said one stationary contact means and said one end of said conductive means during said movement, said auxiliary contact means including means for terminating the bridging of said first gap after said initial part of said movement is exceeded.

2. The combination of claim I and wherein said auxiliary contact means includes an elongated movable electrically conductive component extending into said tubelike holding means.

3. The combination of claim 1 and wherein a spring means is operatively connected with said elongated component of said auxiliary contact means and with said primary contact means for providing movement of said elongated component of said auxiliary contact means with respect to said primary contact means.

4. The combination claim 1 and wherein said conductive means of said primary contact means includes elongated electrically conductive bars the positions of which with respect to each other are determined by said insulating tubular member.

5. The combination of claim 4 and wherein said insulating tubular member has an inner surface formed with axially extending grooves which respectively receive said bars, and said holding means being disposed within said primary contact means and pressing said bars into said grooves.

6. The combination of claim 5 and wherein said holding means is in the form of an elongated metal tube having an exterior surface provided with an outer bead pressing resiliently against said bars, in the manner of a spring, for urging said bars into said grooves.

7. The combination of claim 4 and wherein said insulating tubular member has opposed ends, said bars respectively having opposed ends which curve around said opposed ends of said insulating tubular member.

8. The combination of claim 6 and wherein said metal tube carries at one end a plug of insulating material which closes an end of said insulating tubular member.

9. The combination of claim 35 and wherein said insulating tubular member carries a rounded metallic sleeve at its end which is located at said other stationary contact means when the switch is said switch close position.

10. The combination of claim 35 and wherein said insulating tubular member carries an arc contact sleeve at its end which is located at said one stationary contact means when the switch is in the switch close position.

11. The combination of claim 10 and wherein said insulating tubular member is formed at its inner surface with axially extending grooves, and said conductive means includes elongated electrically conductive bars seated within said grooves, said holding means being a metal tube within said primary contact means having an outer bead engaging said bars and 12. The combination of claim 1 and wherein said cylinder of insulating material is formed with gas-discharge openings, said cylinder otherwise being closed off from the outer atmosphere.

13. The combination'of claim 12 and wherein said cylinder of insulating material has an end directly engaging said one contact means and formed with an interior annular recess communicating with said gas-discharge openings.

14. The combination of claim 13 and wherein said annular recess extends from said end of said cylinder which engages said one contact means axially along said cylinder to an extent approximately equal to one-sixth the diameter of said cylinder.

15. The combination of claim l3 and wherein said tubular member of insulating material is provided at said inner annular recess with a plurality of axially extending projections for engaging said one contact means to center said tubular member for precisely situating the latter coaxially with said one contact means. 1 v

16. The combination of claim I and wherein said one stationary contact means has a region directed toward said other stationary contact means and carrying an elongated tubular insulating covering which surrounds the outer insulating tube of said primary contact means. 7

17. The combination of claim '1 and wherein a swing-lever means of insulating material coacts with said insulating tubular member of said primary contact means for axially shifting the latter, and a rotary drive shaft operatively connected with said swing-lever means for swinging the latter about the axis of said shaft.

18. The combination of claim 17 and wherein said swinglever means has at least one arm formed with an elongated slot passing therethrough, and said insulating tubular member of said primary contact means carrying a metallic slide member received in said slot of said lever means for coacting.

therewith.

19. The combination. of claim 17 and wherein said swinglever means has a pair of arms between whichsaid insulating tubular member of said primary contact means is situated.

20. The combination of claim I and wherein a stationary hollow tube of insulating material is situated at said one convtact means and formed with gas-discharge openings, said stationary tube as well assaid outer insulating tubular member of said primary contact means both being made of polyoxymethylene.

21. The combination of claim 16 and wherein said covering of insulating material is made of polyoxymethylene.

22. The combination of claim 17 and wherein said swinglever means is made of polyoxymethylene.

23. The combination of claim 17 and wherein said swinglever means has a pair of portions extending around said shaft, and clamp means coacting with said portions of said swinglever means for pressing them toward each other to clamp said shaft between said portions of said swing-lever means.

24. The combination of claim 1 including a base member, and a pair of insulating support means for providing for all of said contact means a unipolar current path insulated with respect to ground potential, said pair of support means having respective mounting regions whereat said pair of support means are fixedly mounted to said base member, and said mounting regions of said pair of support means being spaced from each other by a distance which is less than the length of the insulating tube member of said primary contact means.

25. The combination of claim 24 and wherein said pair of support means extend from said fixedly mounted regions thereof angularly away from each other in a plane which contains the axis of said primary contact means.

26. The combination of claim 24 and wherein said pair of support means are identical and symmetrically situated with respect to each other.

27. The combination of claim 1 and wherein both of said stationary contact means are respectively covered with components of insulating material except for exterior surface portions of said pair of stationary contact means which are to be connected with electrical conductors and inner surface portions which respectively coact with said conductive means of said primary contact means.

28. The combination of claim 27 and wherein a pair of insulating support means are provided for supporting said pair of stationary contact means, and a pair of components of insulating material connected with said pair of stationary contact means and connecting the latter to said pair of support means.

29. The combination of claim 28 and wherein said one contact means is formed with undercuts, and said insulatingcomponent which connects said one contact means to one of said insulating support means extending into said undercuts of said one contact means.

30. The combination of claim 29 and wherein an outer covering of insulating material surrounds said outer tube of said primary contact means, said outer covering of insulating material being integral with said insulating component which connects said one contact means with one of said support means.

31. The combination of claim 28 and wherein said component which connects said one contact means to one of said support means has a surface butting against a surface of the latter support means and forming an interface therewith, metallic fasteners fixing said insulating component which connects said one contact means to said one support means against said one support means while providing a pressure at said interface, and said metallic fasteners each being surrounded by an insulating surface extending along an equipotential surface at the region of said interface.

32. The combination of claim 31 and wherein said insulating surface which surrounds each fastener is in the form of a sleeve of insulating material extending across the interface.

33. The combination of claim 28 and wherein all electrically nonconductive components are made of polyoxymethylene.

34. A load disconnect switch comprising an elongated switch-pin structure movable longitudinally between switchclosing and switch-opening positions, two axially spaced and stationary contact members of which one forms a slide contact with which said switch-pin structure is in sliding engagement,

said switch-pin structure forming in said closing position an electrical connection between said two stationary contact members; a current interrupting assembly comprising said stationary slide contact and said switch-pin structure together with two insulating tubes of which one is movable and surrounds said switch-pin structure, said other tube being stationarily connected with said slide contact and extending coaxially around said movable tube, said movable insulating tube being coaxially and fixedly joined with said switch-pin structure; and auxiliary contact means temporarily connecting said switch-pin structure conductively with said other stationary contact member during an initial part of the switch-pin travel from said closing to said opening position.

35. A load disconnect switch, comprising a movable main switch member having an elongated outer insulating tube and an inner tubelike metal structure coaxially fixed to said outer tube, two stationary contact means spaced from each other along the axis of said main member, said movable main member having a switch-closing position and a switch-opening position, the two ends of said tubelike metal structure electrically engaging said respective two stationary contact means when said main member is in said closing position, an auxiliary switching member movable in said tubelike metal structure and bridging at the beginning of the switch opening movement of said main member the separation gap between one end of said tubelike metal structure and one of said stationary contact means, means for quenching the are between the other end of said metal structure and said other stationary contact means, and means for moving said auxiliary switching member into said tubular metal structure so as to open said separation gap between said one end of the latter and said one stationary contact means.

36. The combination of claim 35 and wherein said one stationary contact means has a region directed away from said other stationary contact means, and said are extinguishing means is a cylinder made of insulating material fixedly mounted to said one stationary contact means at said region so as to be coaxial with said primary contact means, so that said cylinder surrounds said primary contact means in said switchopen position. 

1. A load disconnect comprising elongated, primary contact means axially movable between switch-close and switch-open positions, a pair of opposed stationary contact means coaxially arranged with respect to said primary contact means, one of said stationary contact means slidably supporting and guiding said primary contact means for movement between said positions thereof and the other of said stationary contact means being engaged by said primary contact means in said switch-close position, said primary contact means being displaced beyond and out of contact with said other stationary contact means when said primary contact means is in said switch-open position, said primary contact means comprising an insulating tubular member, elongated electrical conductive means disposed in the hollow of said tubular member, said conductive means including tubelike holding means for fixedly holding the same with respect to said tubular member, said conductive means having respective ends, one of said ends directly engaging said one of said stationary contact means and the other one of said ends directly engaging the other one of said stationary contact means when said primary contact means is in the switch-close position thereof, arc extinguishing means disposed on said one stationary contact means and having means for receiving said primary contact means, and auxiliary contact means movably mounted within said tubelike holding means and coacting with said conductive means and said other stationary contact means for temporarily maintaining an electrical connection therebetween by bridging a first gap that forms between said other one of said stationary contact means and said other one of said ends of said conductive means during the initial part of the movement of said primary contact means from said switch-close position to said switch-open position, whereby said primary contact means moves with respect to said arc extinguishing means for developing an air blast to extinguish the arc appearing across a second gap that forms between said one stationary contact means and said one end of said conductive means during said movement, said auxiliary contact means including means for terminating the bridging of said first gap after said initial part of said movement is exceeded.
 2. The combination of claim 1 and wherein said auxiliary contact means includes an elongated movable electrically conductive component extending into said tubelike holding means.
 3. The combination of claim 1 and wherein a spring means is operatively connected with said elongated component of said auxiliary contact means and with said primary contact means for providing movement of said elongated component of said auxiliary contact means with respect to said primary contact means.
 4. The combination claim 1 and wherein said conductive means of said primary contact means includes elongated electrically conductive bars the positions of which with respect to each other are determined by said insulating tubular member.
 5. The combination of claim 4 and wherein said insulating tubular member has an inner surface formed with axially extending grooves which respectively receive said bars, and said holding means being disposed within said primary contact means and pressing said bars into said grooves.
 6. The combinatioN of claim 5 and wherein said holding means is in the form of an elongated metal tube having an exterior surface provided with an outer bead pressing resiliently against said bars, in the manner of a spring, for urging said bars into said grooves.
 7. The combination of claim 4 and wherein said insulating tubular member has opposed ends, said bars respectively having opposed ends which curve around said opposed ends of said insulating tubular member.
 8. The combination of claim 6 and wherein said metal tube carries at one end a plug of insulating material which closes an end of said insulating tubular member.
 9. The combination of claim 35 and wherein said insulating tubular member carries a rounded metallic sleeve at its end which is located at said other stationary contact means when the switch is said switch close position.
 10. The combination of claim 35 and wherein said insulating tubular member carries an arc contact sleeve at its end which is located at said one stationary contact means when the switch is in the switch close position.
 11. The combination of claim 10 and wherein said insulating tubular member is formed at its inner surface with axially extending grooves, and said conductive means includes elongated electrically conductive bars seated within said grooves, said holding means being a metal tube within said primary contact means having an outer bead engaging said bars and resiliently pressing the latter into said grooves, and said arc-contact sleeve extending up to the region of said bead.
 12. The combination of claim 1 and wherein said cylinder of insulating material is formed with gas-discharge openings, said cylinder otherwise being closed off from the outer atmosphere.
 13. The combination of claim 12 and wherein said cylinder of insulating material has an end directly engaging said one contact means and formed with an interior annular recess communicating with said gas-discharge openings.
 14. The combination of claim 13 and wherein said annular recess extends from said end of said cylinder which engages said one contact means axially along said cylinder to an extent approximately equal to one-sixth the diameter of said cylinder.
 15. The combination of claim 13 and wherein said tubular member of insulating material is provided at said inner annular recess with a plurality of axially extending projections for engaging said one contact means to center said tubular member for precisely situating the latter coaxially with said one contact means.
 16. The combination of claim 1 and wherein said one stationary contact means has a region directed toward said other stationary contact means and carrying an elongated tubular insulating covering which surrounds the outer insulating tube of said primary contact means.
 17. The combination of claim 1 and wherein a swing-lever means of insulating material coacts with said insulating tubular member of said primary contact means for axially shifting the latter, and a rotary drive shaft operatively connected with said swing-lever means for swinging the latter about the axis of said shaft.
 18. The combination of claim 17 and wherein said swing-lever means has at least one arm formed with an elongated slot passing therethrough, and said insulating tubular member of said primary contact means carrying a metallic slide member received in said slot of said lever means for coacting therewith.
 19. The combination of claim 17 and wherein said swing-lever means has a pair of arms between which said insulating tubular member of said primary contact means is situated.
 20. The combination of claim 1 and wherein a stationary hollow tube of insulating material is situated at said one contact means and formed with gas-discharge openings, said stationary tube as well as said outer insulating tubular member of said primary contact means both being made of polyoxymethylene.
 21. The combination of claim 16 and wherein said covering of insulating material is made of polyoxymethylene.
 22. The combination of claim 17 and wherein said swing-lever means is made of polyoxymethylene.
 23. The combination of claim 17 and wherein said swing-lever means has a pair of portions extending around said shaft, and clamp means coacting with said portions of said swing-lever means for pressing them toward each other to clamp said shaft between said portions of said swing-lever means.
 24. The combination of claim 1 including a base member, and a pair of insulating support means for providing for all of said contact means a unipolar current path insulated with respect to ground potential, said pair of support means having respective mounting regions whereat said pair of support means are fixedly mounted to said base member, and said mounting regions of said pair of support means being spaced from each other by a distance which is less than the length of the insulating tube member of said primary contact means.
 25. The combination of claim 24 and wherein said pair of support means extend from said fixedly mounted regions thereof angularly away from each other in a plane which contains the axis of said primary contact means.
 26. The combination of claim 24 and wherein said pair of support means are identical and symmetrically situated with respect to each other.
 27. The combination of claim 1 and wherein both of said stationary contact means are respectively covered with components of insulating material except for exterior surface portions of said pair of stationary contact means which are to be connected with electrical conductors and inner surface portions which respectively coact with said conductive means of said primary contact means.
 28. The combination of claim 27 and wherein a pair of insulating support means are provided for supporting said pair of stationary contact means, and a pair of components of insulating material connected with said pair of stationary contact means and connecting the latter to said pair of support means.
 29. The combination of claim 28 and wherein said one contact means is formed with undercuts, and said insulating component which connects said one contact means to one of said insulating support means extending into said undercuts of said one contact means.
 30. The combination of claim 29 and wherein an outer covering of insulating material surrounds said outer tube of said primary contact means, said outer covering of insulating material being integral with said insulating component which connects said one contact means with one of said support means.
 31. The combination of claim 28 and wherein said component which connects said one contact means to one of said support means has a surface butting against a surface of the latter support means and forming an interface therewith, metallic fasteners fixing said insulating component which connects said one contact means to said one support means against said one support means while providing a pressure at said interface, and said metallic fasteners each being surrounded by an insulating surface extending along an equipotential surface at the region of said interface.
 32. The combination of claim 31 and wherein said insulating surface which surrounds each fastener is in the form of a sleeve of insulating material extending across the interface.
 33. The combination of claim 28 and wherein all electrically nonconductive components are made of polyoxymethylene.
 34. A load disconnect switch comprising an elongated switch-pin structure movable longitudinally between switch-closing and switch-opening positions, two axially spaced and stationary contact members of which one forms a slide contact with which said switch-pin structure is in sliding engagement, said switch-pin structure forming in said closing position an electrical connection between said two stationary contact members; a current interrupting assembly comprising said stationary slide contact and said switch-pin structure together with two insulating tubes of which one is movable and surrounds said switch-pin structure, said other tube being stationarily connected with said slide contact and extending coaxially around said movable tube, said movable insulating tube being coaxially and fixedly joined with said switch-pin structure; and auxiliary contact means temporarily connecting said switch-pin structure conductively with said other stationary contact member during an initial part of the switch-pin travel from said closing to said opening position.
 35. A load disconnect switch, comprising a movable main switch member having an elongated outer insulating tube and an inner tubelike metal structure coaxially fixed to said outer tube, two stationary contact means spaced from each other along the axis of said main member, said movable main member having a switch-closing position and a switch-opening position, the two ends of said tubelike metal structure electrically engaging said respective two stationary contact means when said main member is in said closing position, an auxiliary switching member movable in said tubelike metal structure and bridging at the beginning of the switch opening movement of said main member the separation gap between one end of said tubelike metal structure and one of said stationary contact means, means for quenching the arc between the other end of said metal structure and said other stationary contact means, and means for moving said auxiliary switching member into said tubular metal structure so as to open said separation gap between said one end of the latter and said one stationary contact means.
 36. The combination of claim 35 and wherein said one stationary contact means has a region directed away from said other stationary contact means, and said arc extinguishing means is a cylinder made of insulating material fixedly mounted to said one stationary contact means at said region so as to be coaxial with said primary contact means, so that said cylinder surrounds said primary contact means in said switch-open position. 